Geologic maps and sections of the Helen Beryl, Elkhorn, and Tin Mountain pegmatite mines, South Dakota
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Open-File Report↗
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Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.
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Climatologic, soil-water, ground-water, geologic, surface-water, and water-quality data for a surface coal mine in northwestern Colorado
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Open-File Report↗
Geologic setting and water quality of selected basins in the active coal-mining areas of Ohio, 1987-88
This report presents hydrologic data from selected drainage basins in the active coal-mining areas of Ohio from July 1987 through October 1988. The study area is mostly within the unglaciated part of eastern Ohio along the western edge of the Appalachian Plateaus physiographic province. The 1987-88 work is the second phase of a 7-year study to assess baseline water quality in Ohio's coal region. The data collection network consisted of 41 long-term surface-water sites in 21 basins. The sites were measured and sampled twice yearly at low flow. In addition, six individual basins (three each year) selected for a more detailed representation of surface-water and ground-water quality. In 1987, the Sandy Creek, Middle Tuscarawas River and Sugar Creek, and Lower Tuscarawas River basins were chosen. In 1988, the Short and Wheeling Creeks, Upper Wills Creek, and Upper Raccoon Creek basins were chosen. Because of their proximity to the glaciated region and outwash drainage, the basins studied intensively in 1987 contain more shallow productive aquifers than do the basins studied in detail for 1988, in which shallow ground-water sources are very localized. Chemical analyses for 202 surface-water and 24 ground-water samples are presented. For field measurements made at surface-water sites, the specific conductance ranged from 295 to 3150 ? S/cm (microsiemens per centimeter at 25 degrees Celsius). For pH, the range was 2.8 to 8.6. Alkalinity ranged from 5 to 305 mg/L (milligrams per liter) as CaCO3.
Water-Resources Investigations Report↗
Map showing mineral resource potential of the Sierra Ancha Wilderness and Salome Study Area, Gila County, Arizona
The Wilderness Act (Public Law 88-577, Sept. 3, 1964) and certain related Acts require the Geological Survey and the Bureau of Mines to survey certain areas on Federal lands to determine their mineral-resource potential. Results must be made available to the public and be submitted to the Administration and the Congress. These maps and reports present the results of a geologic and mineral survey of the Sierra Ancha Wilderness and Salome Study Area, Gila County, Arizona.
Arizona↗
An overview of mining-related environmental and human health issues, Marinduque Island, Philippines: observations from a joint U.S. Geological Survey - Armed Forces Institute of Pathology reconnaissance field evaluation, May 12-19, 2000
This report summarizes results of a visit by the report authors to Marinduque Island, Philippines, in May 2000. The purpose of the visit was to conduct a preliminary examination of environmental problems created by a 1996 tailings spill from the Marcopper open-pit copper mine. The mine was operated from 1969-1996 by Macropper Mining Corperation, under 39.9% ownership, and design and management control of Placer Dome, Inc. Our trip expenses to and from the Philippines were funded by the USGS. In-country expenses were paid by the offices of Congressman Reyes and the Governor of Marinduque, Carmencita O. Reyes. This report includes observations we made based on our relatively short visit to the island, and observations based upon a preliminary review of the literature available on the islanda??s mining-environmental issues. In addition, we have included preliminary interpretations and analytical results of some water, sediment, and mine waste samples collected during our trip. We also highlight the environmental and human health issues we fell are in need of further study and consideration for mitigation or remediation. This report is preliminary and is not intended to be a comprehensive or final review of the islanda??s mining-environmental issues; many areas of further study are clearly neededa?|
Open-File Report↗
Maps showing mines, quarries, prospects, and exposures in the Devils Fork Roadless Area, Scott County, Virginia
The Wilderness Act (Public Law 88-577, September 3, 1964) and related acts require the U.S. Geological Survey and the U.S. Bureau of Mines to survey certain areas on Federal lands to determine their mineral resource potential. Results must be made available to the public and be submitted to the President and the Congress. This report presents the results of a survey of mines, quarries, prospects, and coal exposures in the vicinity of the Devils Fork Roadless Area in the Jefferson National Forest, Scott County, Virginia. Devils Fork Roadless Area was classified as a further planning area during the Second Roadless Area Review and Evaluation (RARE II) by the U.S. Forest Service, January 1979. The Devils Fork Roadless Area is in the Clinch Ranger district of the Jefferson National Forest, southwestern Virginia. It is located in Scott County, about 5 miles southeast of Big Stone Gap, Virginia, and is accessible from there via U.W. 23 to Duffield, Virginia, and then northeastward along State Route 653 (fig. 1). Access from the north is provided by State Routes 616, 619, and Forest Route 237. Southern access is provided by State Routes 619 and 649. The interior is accessible by foot along overgrown logging railroad grades and abandoned forest roads on the lower portions of Devil Fork, Straight Fork, and Roddy Branch. The Devils Fork Roadless Area is located at the eastern edge of the Appalachian coal region and is within the Cumberland Mountain section of the Appalachian Plateau physiographic province. Most of the area is drained by Devil Fork and its tributaries. Clinch Rock Branch of Straight Creek, Roddy Branch of Valley Creek, and Stinking Creek, all tributary to the Clinch River, drain small fringe tracts. Altitudes range from about 1,550 ft on the lower part of Straight Fork to about 3,490 ft at Cox Place on Little Mountain. Vegetation varies from mixed hardwoods in the uplands to thickets of conifer, rhododendron, and laurel in moist protected areas, as in coves along drainage courses.
Virginia↗
Hydrologic data for Leviathan Mine and vicinity, Alpine County, California, 1981-83
The U.S. Geological Survey collected basic hydrologic and water-quality data during 1981-83 to facilitate the geohydrologic evaluation of the Leviathan Mine area and the design of a pollution-abatement project. Surface-water field data included one or more measurements of pH, water temperature, and specific conductance at 45 sites in and adjacent to the mine area. At nine of these sites, daily data on discharge, specific conductance, and water temperature were collected during parts of 1981-82 by using electronic monitor-recorder systems. Ground-water field data included one or more of the water-quality measurements listed above at 71 piezometers in the mine area. Borehole geophysical data included neutron-moisture, neutron-porosity, gamma-gamma density, natural gamma, and temperature logs at three sites. Mineralogic and hydrologic data were obtained for cores taken from nine test holes. One or more surface-water samples from 26 sites were analyzed for major cations, major anions, and a wide range of minor inorganic constituents. Single ground-water samples from 36 piezometers were analyzed for the same array of major and minor constituents. (USGS)
Open-File Report↗
Questa baseline and pre-mining ground-water quality investigation 22 — Groundwater budget for the Straight Creek drainage basin, Red River Valley, New Mexico, with a section on Sulphur Gulch water budget
In April 2001, the U.S. Geological Survey (USGS) and the New Mexico Environment Department (NMED) began a cooperative study to infer the pre-mining ground-water chemistry at the Molycorp molybdenum mine site in the Red River Valley. The Molycorp mine has been in operation since the 1920s. Because ground-water conditions prior to mining are not available, sites analogous to the pre-mining conditions at the mine site must be studied to infer those pre-mining conditions. The Straight Creek drainage basin (watershed) was selected as the primary analog site for this study because of its similar terrain and geology to the mine site, accessibility, potential for well construction, and minimal anthropogenic activity. The purpose of this report is to present results of a water-budget analysis of the debris-flow aquifer in the Straight Creek watershed. The water budget is based on mean annual conditions and is assumed to be steady state. For this study, the Straight Creek watershed was divided into sub-watersheds on the basis of locations of seismic lines, which were used to calculate cross-section area through the Straight Creek debris-flow deposits and underlying fractured and weathered bedrock (regolith). Water-budget components were calculated for areas upstream from and between the seismic lines. Components of the water budget were precipitation, evapotranspiration, surface-water flow, and ground-water flow under a steady-state mean annual condition. Watershed yield, defined as precipitation minus evapotranspiration, was separated into surface-water flow, ground-water flow through the debris-flow deposits and regolith, and ground-water flow through fractured bedrock. The approach to this calculation was to use Darcy's Law to calculate the flow through the cross-section area of the saturated debris-flow deposits and underlying regolith as defined by the interpreted seismic data. The amount of watershed yield unaccounted for through this section then was attributed to either surface-water flow or the component of ground-water flow through fractured bedrock. The inflow to the watershed, calculated to be 701 gallons per minute, is from precipitation. The calculated outflow from the watershed at or upstream from seismic-line 5 (the downstream-most line in Straight Creek prior to entering the Red River Valley) is 540 gallons per minute of evapotranspiration in the watershed upstream from line 5 (77.0 percent of precipitation), 5 gallons per minute of surface-water flow (0.7 percent of precipitation), 122 gallons per minute of ground-water flow through the debris-flow deposits and underlying regolith defined by the seismic data (17.4 percent of precipitation), and 34 gallons per minute of ground-water flow through fractured bedrock below the defined seismic line (4.9 percent of precipitation). The ground-water flow through the alluvium and inter-tonguing debris-flow deposits of the Red River Valley was calculated to be 5,227 gallons per minute at seismic-line 7, the first seismic line in the Red River Valley downstream from Straight Creek. The water budget indicates the amount of ground-water flow that enters the Red River alluvium from the debris-flow deposits and regolith in Straight Creek is small (about 2.3 percent; 122 gallons per minute) compared to the volume of flow that moves through the Red River alluvium. The total amount of ground-water flow from Straight Creek (156 gallons per minute; 122 gallons per minute from debris-flow deposits and regolith plus 34 gallons per minute through fractured bedrock) is about 3.0 percent of the ground-water flow calculated at line 7 for the Red River alluvium.
New Mexico↗
Maps showing mines, quarries, prospects, and exposures in the Cheat Mountain Roadless Area, Randolph County, West Virginia
The Wilderness Act (Public Law 88-577, September 3, 1964) and related acts require the U.S. Geological Survey and the U.S. Bureau of Mines to survey certain areas on Federal lands to determine their mineral resource potential. Results must be made available to the public and be submitted to the President and the Congress. This report presents the results of a mineral survey of the Cheat Mountain Roadless Area in the Monongahela National Forest, Randolph County, West Virginia. The area was designated as a further planning area during the Second Roadless Area Review and Evaluation (RARE II) by the U.S. Forest Service, January 1979. The Cheat Mountain Roadless Area is in the Greenbrier Ranger District of the Monongahela National Forest, east-central West Virginia. It is located in Randolph County about 10 mi southeast of Elkins, W.Va., and is accessible there via U.S. 219-250 to Beverly, W.Va., and then southeastward along an improved country road. From the east, the study area can be reached via U.S. 33 and by a paved country road that extends from Alpena, W.Va. to the village of Bemis. Unimproved Forest service roads, abandoned logging railroad grades, and primitive trails provide access by foot or horseback into the interior of the study area. Physiographically, the Cheat Mountain Roadless Area is in the Allegheny Mountain section of the Appalachian Plateaus province and is situated at the eastern edge of the Appalachian coal region. Cheat Mountain, a northeast-trending ridge, is bordered on the west by the right fork of Files Creek and on the east by Shavers Fork and its tributaries. Most of the area occupies an elevated plateau capped by resistant sandstone and conglomerate. Altitudes range form 2,320 ft on Lime Kiln Run to more than 3,900 ft on Cheat Mountain. The topography ranges from relatively flat in the uplands to very steep in the canyons along tributaries of Shavers Fork. The area is heavily forested with vegetation varying from mixed hardwoods on the western slope of Cheat Mountain to thickets of conifers in the uplands. Hemlocks are sparsely interspersed and red spruce, the dominant tree at higher elevations prior to logging in the mid 1920's, is again reforesting upland areas. Rhododendron and laurel flourish in moist protected areas along drainage courses and in coves.
West Virginia↗
Quality of surface water in the coal-mining region, southwestern Indiana, October 1979 to September 1980
The U.S. Geological Survey collected water-quality and other hydrologic data for surface water in the coal-mining region of southwestern Indiana. These data were collected at 85 sites in 19 counties during October 1979 and at 21 of the 85 sites in 12 of the 19 counties monthly from January through September 1980. The samples were collected during steady flow. Samples were also collected at 8 of the 21 monthly sites during unsteady flow caused by storms. Samples were collected prestorm; on the rising, peak, and falling stream stages; and poststorm, after flow had stabilized. Water samples were collected at each site for determining concentrations of major ions, selected metals, nutrients, and suspended sediment. Specific conductance, pH, water temperature, dissolved oxygen, and instantaneous discharge were also determined at each site. During October 1979, streambed-material samples were collected at 74 sites for determining concentrations of acid-soluble constituents on sediment smaller than 63-micron diameter. During March 1980, streambed-material samples were collected at 14 sites for determining the quantity of coal in streambed sediments.
Indiana↗
Resistivity‐studies of some salt‐water boundaries in the Hawaiian Islands
In the course of a systematic survey of the ground‐water resources of the Hawaiian Islands which is being made under the direction of H. T. Stearns of the United States Geological Survey in cooperation with the Territorial Government of Hawaii, it was found desirable to test the utility of geophysical methods in the solution of certain Hawaiian water‐supply problems. A cooperative geophysical survey for this purpose was undertaken by the Geophysical Section, then with the Bureau of Mines but later transferred to the Geological Survey, during the course of which a series of resistivity‐studies of certain salt‐water boundaries was begun. Since the location of such boundaries is of considerable importance in many areas it has been thought worth while to present the results which have thus far been obtained.
Eos, Transactions, American Geophysical Union↗
Maps showing mines, quarries, prospects, and exposures in the Otter Creek Wilderness, Randolph and Tucker counties, West Virginia
The Wilderness Act (Public Law 88-577, September 3, 1964) and related acts require the U.S. Geological Survey and the U.S. Bureau of Mines to survey certain areas on Federal lands to determine their mineral resource potential. The act also directs that results of such surveys be made available to the public and be submitted to the Administration and the Congress. This report presents a part of the results of a mineral survey of the Otter Creek Wilderness, Randolph and Tucker counties, West Virginia, which was established as a wilderness by Public Law 93-622, January 3, 1975.
West Virginia↗
Mines, prospects, and mineral sites, wilderness and RARE II areas, White Mountain National Forest, New Hampshire
The Wilderness Act (Public Law 88-577, September 3, 1964) and related acts require the U.S. Geological Survey and the U.S. Bureau of Mines to survey certain areas on Federal lands to determine their mineral value, if any, that may be present. Results must be made available to the public and be submitted to the President and the Congress. This report presents the results of investigations of mines, prospects, and mineral sites in the Great Gulf and Presidential Range-Dry River Wilderness Areas; the Dartmouth Range, Wild River, Pemigewasset, Kinsman Mountain, Mount Wolf-Gordon Pond, Jobildunk, and Carr Mountain Roadless Areas; and the intervening and immediately surrounding areas in the White Mountain National Forest, Coos, Grafton, and Carroll Counties, New Hampshire. The Great Gulf Wilderness was established when the Wilderness Act was passed in 1964, and the Presidential Range-Dry River Wilderness was established by Public Law 93-622, January 3, 1975. The Dartmouth Range, Wild River, Pemigewasset, Kinsman Mountain, Mount Wolf-Gordon Pond, Carr Mountain, and Jobildunk areas were classified as a further planning area during the Second Roadless Area Review and Evaluation (RARE II) by the U.S. Forest Service, January 1979. The areas investigated are located in the White Mountain National Forest in Coos, Grafton, and Carroll Counties, New Hampshire. Personnel from the U.S. Bureau of Mines conducted field reconnaissance of the westernmost areas, Kinsman Mountain, Mt. Wolf-Gordon Pond, Jobildunk, and Carr Mountain, in the fall of 1980. Field reconnaissance of the eastern areas, Great Gulf, Presidential Range-Dry River, Dartmouth Range, Pemigewasset and Wild River was conducted in the spring of 1981. A total of 237 rock and 103 panned-concentrate samples were collected during the investigations. Reconnaissance radiometric ground surveys were conducted at selected locations.
New Hampshire↗
Mapping known and potential mineral occurrences and host rocks in the Bonnifield Mining District using minimal cloud- and snow-cover ASTER data: Chapter E in Recent U.S. Geological Survey studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada--results of a 5-year project
On July 8, 2003, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor acquired satellite imagery of a 60-kilometer-wide swath covering a portion of the Bonnifield mining district within the southernmost part of the Tintina Gold Province, Alaska, under unusually favorable conditions of minimal cloud and snow cover. Although rocks from more than eight different lithotectonic terranes are exposed within the extended swath of data, we focus on volcanogenic massive sulfides (VMS) and porphyry deposits within the Yukon-Tanana terrane (YTT), the largest Mesozoic accretionary terrane exposed between the Denali fault system to the south of Fairbanks and the Tintina fault system to the north of Fairbanks. Comparison of thermal-infrared region (TIR) decorrelation stretch data to available geologic maps indicates that rocks from the YTT contain a wide range of rock types ranging in composition from mafic metavolcanic rocks to felsic rock types such as metarhyolites, pelitic schists, and quartzites. The nine-band ASTER visible-near-infrared region--short-wave infrared region (VNIR-SWIR) reflectance data and spectral matched-filter processing were used to map hydrothermal alteration patterns associated with VMS and porphyry deposit types. In particular, smectite, kaolinite, opaline silica, jarosite and (or) other ferric iron minerals defined narrow (less than 250-meter diameter) zonal patterns around Red Mountain and other potential VMS targets. Using ASTER we identified some of the known mineral deposits in the region, as well as mineralogically similar targets that may represent potential undiscovered deposits. Some known deposits were not identified and may have been obscured by vegetation or snow cover or were too small to be resolved.
Alaska;Yukon↗
Paleoslumps in coal-bearing strata of the Breathitt Group (Pennsylvanian), Eastern Kentucky Coal Field, U.S.A
The benefits of geologic analysis for roof-control studies and hazard prediction in coal mines are well documented. Numerous case studies have illustrated the importance of recognizing geologic features such as paleochannels, coal riders, and kettlebottoms in mine roofs. Relatively understudied features, in terms of mining, are paleoslumps .Paleoslumps represent ancient movement and rotation of semi-consolidated sediment. Because bedding in paleoslumps is deformed or inclined, these features cause instability in mine roofs, haul roads, surface highwalls, and other excavations. Various types of paleoslumps above coals in the Eastern Kentucky Coal Field were studied in order to aid in their recognition and prediction in mines. The paleoslumps studied all showed characteristic slump-deformation features, although some differences in magnitude of deformation and overall slump size were noted. Coals beneath slumps often exhibited folding, reverse displacements, truncation, clastic dikes, and locally increased thickness. Slumps are inferred to have been triggered by a wide range of mechanisms, such as loading of water-saturated sediment on rigid substrates, synsedimentary faulting, and over-pressurization of channel margin and bar slopes. Analysis of paleoslumps in underground mines, where paleoslumps are viewed from beneath rather than in profile is difficult, since characteristic bed rotation may not be conspicuous. Sudden increases in bed-dip angle inferred from changes in rock type or bedding contacts in the roof; occurrence of bounding, polished rotation surfaces; or roof irregularity and occurrence of loading features may indicate the presence of paleoslumps. Another key to recognition may be the sudden appearance of over-thickened coal, which can occur because of slump-created paleotopography, synsedimentary faults, and slump-generated overthrusting. In addition, steeply inclined, folded, or transported coal marginal to paleoslumps can create apparent increases in coal thickness in cores. Although thick coals are obviously a target of exploration, anomalously thick coals may actually indicate adjacent paleoslumps accompanied by hazardous roof conditions and loss of seam thickness.
International Journal of Coal Geology↗
Applied Geochemistry Special Issue on Environmental geochemistry of modern mining
Environmental geochemistry is an integral part of the mine-life cycle, particularly for modern mining. The critical importance of environmental geochemistry begins with pre-mining baseline characterization and the assessment of environmental risks related to mining, continues through active mining especially in water and waste management practices, and culminates in mine closure. The enhanced significance of environmental geochemistry to modern mining has arisen from an increased knowledge of the impacts that historical and active mining can have on the environment, and from new regulations meant to guard against these impacts. New regulations are commonly motivated by advances in the scientific understanding of the environmental impacts of past mining. The impacts can be physical, chemical, and biological in nature. The physical challenges typically fall within the purview of engineers, whereas the chemical and biological challenges typically require a multidisciplinary array of expertise including geologists, geochemists, hydrologists, microbiologists, and biologists. The modern mine-permitting process throughout most of the world now requires that potential risks be assessed prior to the start of mining. The strategies for this risk assessment include a thorough characterization of pre-mining baseline conditions and the identification of risks specifically related to the manner in which the ore will be mined and processed, how water and waste products will be managed, and what the final configuration of the post-mining landscape will be. In the Fall 2010, the Society of Economic Geologists held a short course in conjunction with the annual meeting of the Geological Society of America in Denver, Colorado (USA) to examine the environmental geochemistry of modern mining. The intent was to focus on issues that are pertinent to current and future mines, as opposed to abandoned mines, which have been the focus of numerous previous short courses. The geochemical challenges of current and future mines share similarities with abandoned mines, but differences also exist. Mining and ore processing techniques have changed; the environmental footprint of waste materials has changed; environmental protection has become a more integral part of the mine planning process; and most historical mining was done with limited regard for the environment. The 17 papers in this special issue evolved from the Society of Economic Geologists’ short course. The relevant geochemical processes encompass the source, transport, and fate of contaminants related to the life cycle of a mine. Contaminants include metals and other inorganic species derived from geologic sources such as ore and solid mine waste, and substances brought to the site for ore processing, such as cyanide to leach gold. Factors, such as mine-waste mineralogy, hydrologic setting, mine-drainage chemistry, and microbial activity, that affect the hydrochemical risks from mining are reviewed by Nordstrom et al. In another paper, Nordstrom discusses baseline characterization at mine sites in a regulatory framework, and emphasizes the influence of mineral deposits in producing naturally elevated concentrations of many trace elements in surface water and groundwater. Surface water quality in mineralized watersheds is influenced by a number of processes that act on daily (diel) cycles and can produce dramatic variations in trace element concentrations as described by Gammons et al. Pre-mining baseline characterization studies should strive to capture the magnitude of these diel variations. Desbarats et al., using a case study of mine drainage from a gold mine, illustrate how elements that commonly occur as negatively charged species (anions) in solution, such as arsenic as arsenate, behave in an opposite fashion than most metals, which occur as positively charged species (cations). Significant improvement in the understanding of factors that influence the toxicity of metals to aquatic organisms in surface water has highlighted the importance of aqueous chemistry, particularly dissolved organic carbon, as described by Smith et al. Stream sediment contamination is another important pathway for affecting aquatic organisms, as reviewed by Besser et al. Understanding and predicting environmental consequences from mining begins with knowing the mineralogy and mineral reactivity of the ore, the wastes, and of secondary minerals formed later. Jamieson et al. review the importance of mineralogical studies in mine planning and remediation. A number of types of site-specific studies are needed to identify environmental risks related to individual mines. Lapakko reviews the general framework of mine waste characterization studies that are integral to the mine planning process. Hageman et al. present a comparative study of several static tests commonly used to characterize mine waste. The mining and ore processing practices employed at a specific mine site will vary on the basis of the commodities being targeted, the geology of the deposit, the geometry of the deposit, and the mining and ore processing methods used. Thus, these factors, in addition to the waste management practices used, can result in a variety of end-member mine waste features, each of which has its own set of challenges. Open pit mines and underground mines require waste rock to be removed to access ore. Waste rock presents unique problems because the rock is commonly mineralized at sub-economic grades and has not been processed to remove potentially problematic minerals, such as pyrite. Amos et al. examine the salient aspects of the geochemistry of waste rock. Mill tailings – the waste material after ore minerals have been removed – are a volumetrically important solid waste at many mine sites. Their fine grain size and the options for their management make their behavior in the environment distinct from that of waste rock. Lindsay et al. describe some of these differences through three case-study examples. Subaqueous disposal of tailings is another option described by Moncur et al. Cyanide leaching for gold extraction is a common method throughout the world. Johnson describes environmental aspects of cyanidation. Uranium mining presents unique environmental challenges, particularly since in-situ recovery has seen widespread use. Campbell et al. review the environmental geochemistry of uranium mining and current research on bioremediation. Ore concentrates from many types of metal mining undergo a pyrometallurgical technique known as smelting to extract the metal. Slag is the result of smelting, and it may be an environmental liability or a valuable byproduct, as described by Piatak et al. Finally, the open pits that result from surface mining commonly reach below the water table. At the end of mining, these pits may fill to form lakes that become part of the legacy of the mine. Castendyk et al., in two papers, review theoretical aspects of the environmental limnology of pit lakes. They also describe approaches that have been used to model pit lake water balance, wall-rock contributions to pit lake chemistry, pit lake water quality, and limnological processes, such as vertical mixing, through the use of three case studies.
Applied Geochemistry↗
Aeromagnetic and magnetotelluric imaging of west-central Idaho and the Stibnite-Yellow Pine mining district: A regional to district perspective
Aeromagnetic and magnetotelluric (MT) data are used to better understand the geology and mineral resources near the Stibnite-Yellow Pine mining district in central Idaho. The reduced-to-pole (RTP) transformation of regional-scale aeromagnetic data shows that allochthonous island-arc rocks west of the Salmon River suture are significantly more magnetic than the Laurentian continental rocks east of the suture and that the granitoids of the Idaho batholith have moderate to low magnetization in both early, metaluminous, and late, peraluminous phases. Application of tilt derivative to aeromagnetic data highlights major crustal-scale structures. The 5-km upward continued magnetic data indicate island-arc rocks have deep magnetic sources. The 110-km-long MT profile images resistivity structure to depths around 30 km. At shallow depths, resistivity corresponds to mapped geologic units, with moderate resistivities underlying volcanic and roof-pendant metasedimentary rocks and moderate to high resistivities occurring beneath the Idaho batholith. Crustal-scale moderate resistivities beneath the suture image the results of tectonomagmatic processes that accompanied suturing and translating allochthonous terranes. Low resistivity values beneath and fringing the batholith are derived from metasedimentary rocks that may have served as a melt source and reductant during melt generation and provided metals during later ore formation. In the Stibnite-Yellow Pine mining district, a high-resolution aeromagnetic compilation is shown to correlate with mapped lithologies and mineral deposit-related structures. The RTP transform distinguishes magnetic and nonmagnetic granitoid phases of the Idaho batholith. The tilt derivative highlights metasedimentary rocks, some of which are favorable ore hosts. The Meadow Creek fault hosts the Stibnite and Hangar Flats deposits and is imaged as a magnetic low due to hydrothermal alteration. Reconstructions of magnetic anomaly offsets and orebodies indicate around 3 km of post-95 Ma dextral separation, with some or all of the offset inferred to postdate the main Au mineralization episode (61–66 Ma).
Idaho↗
Report on progress of investigations of mineral resources of Alaska in 1904
During the last two years the United States Geological Survey has met the demand of the mining public for early publication of economic results by issuing an annual bulletin entitled "Contributions to Economic Geology." Though these volumes have made no attempt to treat exhaustively any of the subject discussed, and while many of the included papers have been but the barest outlines, they have met a cordial reception from those interested in developing the mineral resources of the country. Among the many papers in these bulletins were a number devoted to the mineral deposits of Alaska. In view of the rapid extension of the Alaskan work of the Geological Survey and its segregation in a distinct division, it has seemed desirable to issue a separate publication containing the papers summarizing the previous year's work.
Alaska↗